Smart phones are fast replacing home computers for many daily online activities. But 39 percent of the more than 100 million American adult smart phone owners failed to take even minimal security measures to protect their phone, the latest Consumer Reports State of the Net survey found. The survey projects that at least 7.1 million phones were irreparably damaged, lost, or stolen and not recovered last year.

Here are some examples of how few users protected their phones:

36 percent used a screen-lock of any kind (4 digits or stronger).

31 percent had backed-up their data, such as photos or contacts.

22 percent had installed software that could locate a missing phone.

7 percent had installed software that could erase the contents of a missing phone.

Other highlights from our findings include:

Malicious software is a real threat to smart phones. Last year, 5.6 million users experienced symptoms of such software, our survey projects.

Many users who wanted to turn off their phone's location-tracking feature to protect their privacy didn't know how to do so. For instructions on how to disable location tracking, as well as other phone security tips, see our video.

Apps are often too intrusive. Roughly 48 million users had stopped installing an app last year because it requested too many privileges, our survey suggests. To try your hand at spotting intrusive apps, try our interactive quiz.